It is predicted that the usage of compact magnetic sensors will expand increasingly. Particularly, it is thought that an electric power measuring device is an essential device in the case of intending to utilize electric energy from fossil fuel. Patent Literature 1 discloses an electric power measuring device that connects a magnetic sensor and a sensor resistance in series, installs the magnetic sensor and the sensor resistance so as to be parallel to a load in an electric circuit and further to be adjacent to a wire of the electric circuit, and thereby, can measure the consumed electric power in the load.
Such an electric power measuring device can be formed such that the size is mostly the size of a magnetic thin film, and therefore, can be made such that the element, as a whole, has a size of approximately several millimeters square. Therefore, by installing the device at each of various spots in a large-scale system, it is possible to minutely monitor the consumed electric power.
Meanwhile, as the usage expands, there is a possibility that an intended use environment is a harsh environment. Particularly, it is known that magnetic characteristics change depending on temperature, and for the accuracy enhancement of the sensor sensitivity, temperature compensation is an indispensable technology for the magnetic sensor.
In view of this problem, Patent Literature 2 discloses a technology in which the magnetoresistance effects in different temperature environments have a predetermined relation to a magnetic field to be applied and thereby a constant temperature compensation becomes possible.
Among magnetic sensors utilizing magnetism, a magnetic sensor utilizing the magnetoresistance effect is particularly referred to as a magnetoresistance effect type magnetic sensor. The magnetoresistance effect type magnetic sensor detects the magnitude of a measurement-target magnetic field given in the orthogonal direction to a direction in which an electric current flows. Then, a magnetic field to be previously given in the same direction as the measurement-target magnetic field for the detection is referred to as a bias magnetic field.
Patent Literature 2 mentions the relation between the magnitude of the bias magnetic field and the magnetoresistance effect. However, as for the bias magnetic field in Patent Literature 2, the magnetic field to be given to the magnetic sensor decreases when a concave part of a rotor of a measurement object comes close, and the magnetic field to be given to the magnetic sensor increases when a convex part comes close. That is, the bias magnetic field mentioned in Patent Literature 2 is virtually the applied magnetic field (measurement-target magnetic field) for the magnetic sensor, and is not the bias magnetic field for determining the operating point of the magnetic sensor.